In general, a hydraulic excavator as a construction machine is roughly composed of an automotive lower traveling structure by a traveling motor, an upper revolving structure rotatably mounted on the lower traveling structure and provided with a prime mover for driving a hydraulic motor, and a front device provided on the upper revolving structure moved upward/downward by an actuator.
Here, the upper revolving structure is provided with a revolving frame forming a support structural body, and a control valve block mounting plate is provided on the revolving frame. A control valve block composed of a collective body of a plurality of directional control valves is mounted on this control valve block mounting plate, and supply/discharge of pressurized oil from a hydraulic pump to the traveling motor and the actuator is controlled by each of directional control valves constituting this control valve block. The configuration is such that operations of the traveling motor and the actuator can be controlled by supplying a pilot pressure according to operations of a lever, a pedal and the like to each of the directional control valves constituting the control valve block (see, Patent Document 1, for example).